Jmonkey engine 3.0 Drawing points

Question

How can I draw a 3D-point (or point sprite) in 3D space?

There is no documentation for drawing a point in JMonkey Engine site or anywhere else. Just a single point. Then updating the coordinates. No color, just a dot in 3D space.

Answer 1

A point (as opposed to a sphere) can be created using a mesh in which you directly set its buffers (or technically buffer; since a points mesh doesn't require an index buffer as other more complex meshes require. See How can I draw a straight line in the JMonkey Engine library). Mesh creation is documented here.

An example of creating points in 3D space using a mesh is below:

import com.jme3.app.SimpleApplication;
import com.jme3.material.Material;
import com.jme3.math.*;
import com.jme3.renderer.RenderManager;
import com.jme3.scene.*;
import com.jme3.util.BufferUtils;

public class Main extends SimpleApplication {

    public static void main(String[] args) {
        Main app = new Main();
        app.start();
    }

    @Override
    public void simpleInitApp() {

        Vector3f[] lineVerticies=new Vector3f[5];

        lineVerticies[0]=new Vector3f(2,0,0);
        lineVerticies[1]=new Vector3f(-1,0,1);
        lineVerticies[2]=new Vector3f(0,1,1);
        lineVerticies[3]=new Vector3f(1,1,1);
        lineVerticies[4]=new Vector3f(1,4,0);

        plotPoints(lineVerticies,ColorRGBA.White);
    }


    public void plotPoints(Vector3f[] lineVerticies, ColorRGBA pointColor){
        Mesh mesh = new Mesh();
        mesh.setMode(Mesh.Mode.Points);


        mesh.setBuffer(VertexBuffer.Type.Position, 3, BufferUtils.createFloatBuffer(lineVerticies));


        mesh.updateBound();
        mesh.updateCounts();

        Geometry geo=new Geometry("line",mesh);
        Material mat = new Material(assetManager, "Common/MatDefs/Misc/Unshaded.j3md");
        mat.setColor("Color", pointColor);
        geo.setMaterial(mat);



        rootNode.attachChild(geo);
    }


    @Override
    public void simpleUpdate(float tpf) {
        //TODO: add update code
    }

    @Override
    public void simpleRender(RenderManager rm) {
        //TODO: add render code
    }
}

This will create the points within pointVerticies as shown below

Later if you need to update infomation in a buffer you can do so using:

VertexBuffer posBuffer = mesh.getBuffer(Type.Position);
posBuffer.updateData(BufferUtils.createFloatBuffer(newData));
posBuffer.setUpdateNeeded();
mesh.updateCounts();
mesh.updateBound();

Or (much more efficiently) you can just attach your geometry to a node and move that (depending on your usage case).

Notes
In its most basic state the Vertex buffer expects x1,y1,z1,x2,y2,z2,x3.... etc with no demarcation between where one vertex ends and the other begins. So the following would enter 3 vertices into the buffer; (1.1,1.2,1.3), (2.1,2.2,2.3) and (3.1,3.2,3.3)

m.setBuffer(VertexBuffer.Type.Position, 3, new float[]{1.1,1.2,1.3,2.1,2.2,2.3,3.1,3.2,3.3});

However the createFloatBuffer() method converts from an array of Vector3f into this form.

Also; its often possible to 'get away with' not calling mesh.updateBound();, however without it objects may be culled because the graphics card believes them to be off screen when actually they are visible